This invention relates to vehicle drive train systems which incorporate plunging type constant velocity universal joints. Additionally this invention relates to an improved structure for a plunging constant velocity universal joint.
Universal joints are commonly used in the drive train systems of automotive vehicles. A universal joint is a mechanical coupling device which provides a rotational driving connection between two rotatable shafts, while permitting such shafts to be oriented at an angle relative to one another. For example, a universal joint is commonly used to provide a rotational driving connection between a rear end of a drive shaft (sometimes referred to as a propeller shaft) rotatably driven by a vehicle engine (via a transmission) and an input shaft connected to the vehicle rear axle is assembly (sometimes referred to as a differential input shaft). This is because the drive shaft and the rear axle assembly input shaft are rarely coaxially aligned. To accommodate this non-alignment, while still providing a rotational driving connection, a universal joint is provided therebetween.
Universal joints are commonly classified by their operating characteristics. One important operating characteristic relates to the relative angular velocities of the two shafts connected thereby. In a constant velocity type of universal joint, the instantaneous angular velocities of the two shafts are always equal, regardless of the angle of rotation. In a non-constant velocity type or Cardan universal joint, the instantaneous angular velocities of the two shafts vary with the angle of rotation (although the average angular velocities for a complete rotation are equal).
A typical structure for a constant velocity universal joint includes a cylindrical inner race connected to one of the shafts and a hollow cylindrical outer race connected to the other of the shafts. The inner race fits concentrically within the outer race. The inner and outer races are mounted for angular articulation with respect to each other. The outer surface of the inner race and the inner surface of the outer race have respective pluralities of grooves formed therein. The grooves extend linearly and have generally semi-circular or other curvilinear cross sectional shapes. Each groove formed in the outer surface of the inner race is associated with a corresponding groove formed in the inner surface of the outer race. A ball is disposed in each of the associate pairs of grooves. The balls provide a driving connection between the inner and outer races, i.e., the ball provide a positive driving torque connection so that rotation of one of the inner or outer races results in rotation of the other of the inner and outer races. An annular cage is typically provided between the inner and outer races for retaining the balls in the grooves. The cage is provided with a plurality of circumferentially spaced openings for this purpose.
In one known variety of the ball and cage type of constant velocity universal joint, the grooves formed in the outer surface of the inner race are oriented so as to be alternately inclined relative to the rotational axis of the joint, i.e., the grooves on the surface of the inner race are not parallel to the axis of the inner race . Similarly, the grooves formed in the inner surface of the outer race are alternately inclined relative to the rotational axis of the outer race. For each pair of associated inner and outer race grooves, the inner race groove is inclined in one direction relative to the rotational axes of the joint, while the outer race groove is inclined in the opposite direction. Joints having this orientation of the two different sets of grooves is commonly referred to as a cross groove constant velocity joint.
Known cross groove joints permit relative axial movement between the inner race and the cage, as well as between the cage and the outer race. Thus, the center of the joint (which is defined by the point of intersection of the rotational axis of the two shafts connected thereto) can move axially during use. A design of a universal joint structure that allows relative axial movement between the inner and outer race is useful because distance variations between the transmission and the axle assembly occurring during the normal flexing of the vehicle frame can be reconciled. Further, distance variations resulting from vehicle jounce and rebound can also be reconciled. Universal joints such as cross groove joints that allow axial movement of the two shafts are commonly referred to as plunging constant velocity universal joints. Because there is no physical engagement between the inner race and the cage or between the cage and the outer race, cross groove joints have been found to be well suited for high rotational speed applications.
In many rear wheel drive vehicle applications the drive shaft is not only non-aligned with the input shaft of the rear axle assembly but is also non-aligned with an output shaft of the transmission. Therefore two universal joints will be utilized. A front or forward universal joint will join the transmission output shaft to a front end of the drive shaft. A second or rearward universal joint will join the input shaft of the rear axle assembly to a rear end of the drive shaft.
The vehicle engine and transmission are rigidly fixed to a flame of the vehicle. However the rear axle assembly is connected to the frame via a suspension system. Therefore the rear axle assembly's position with respect to the vehicle frame, engine and transmission is not fixed and can often change with movement or dynamic loading of the vehicle. To accommodate the change of position of the rear axle assembly with respect to the transmission it is preferable that plunging constant velocity joints be utilized to connect the drive shaft with the transmission output shaft and the rear axle assembly input shaft. The aforementioned arrangement allows the drive shaft to translate along its axis within limits imposed by the two plunging constant velocity universal joints.
In vehicle drive trains wherein the drive shaft is connected to two plunging constant velocity universal joints, rapid accelerations can cause the drive shaft to violently plunge to the limit of travel of one of the constant velocity universal joints. The violent travel of the drive shaft generates an undesirable noise condition and adds wear to seals of the joint.
An attempt to rectify the above noted problem has been made by adding a spring to one of the joints. The spring was used to limit the travel of the drive shaft. However the added spring did not solve the problem because the amount of resistance to rapid movement is limited to the spring constant. The added spring provides resistance inhibiting drive shaft travel, but does not prevent violent movement of the drive shaft.